Ting Zhang, Wei-dong Fu, Rui-hai Zhang, Zhen Song, Chao Bai, Cheng-cheng Huang and Guo-liang Zhang
Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences, Beijing 100081, China
Cenchrus spinifex is an invasive plant found in large areas of northern China. In this study, we focused on analyzing the effects of C. spinifex on soil nitrogen and plant nitrogen pools in Horqin sandy grassland. In addition, a pot experiment with 15N tracing techniques was designed to study the biological nitrogen fixation ability of C. spinifex, compared with two native grasses (Elymus dahuricus and Agropyron cristatum). The total soil nitrogen pool in the C. spinifex invaded-area compared with those in bare and native plant Roegneria kamoji areas significantly increased by 47.5% and 20.8% while the soil ammonium nitrogen decreased significantly by 25.6% and 25.2%, respectively. The plant shoot nitrogen pool decreased significantly by 12.8% in C. spinifex compared with the native plant R. kamoji. Atom% 15N, atom% 15N excess and atom% 15N weighting excess of C. spinifex were all significantly lower than those of E. dahuricus and A. cristatum. The nitrogen utilization of C. spinifex and E. dahuricus were 48.5% and 47.0%, respectively, and no significant differences were observed. The C. spinifex nitrogen-fixing percentage was 60.2% compared with E. dahuricus. These results suggested that the adaption to sandy grassland of this invasive weed might be due to its high efficient utilization of nitrogen, leading to successful colonization and spread in Horqin Steppe.